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Old 25th May 2021, 1:33 pm   #8
Robert Gribnau
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Join Date: May 2017
Location: The Hague, The Netherlands
Posts: 231
Default Re: Advice on this linestage build

The EF86 was designed for low level audio applications. It has a bifilar filament (like the EF40 and the CF50 before it) to minimize heater hum. With respect to noise and microphonics I think they are rather good. The EF86's I use in the first stage of two of my guitar amplifiers are not prone to microphonics (but they are stand-alone amplifiers and the filaments are being fed dc voltage).

The EF184 was designed for the IF stages of televisions, so also mostly for low level signals. But they were not designed with audio in mind (as far as I know, they do not have bifilar filaments). I know that Radford used them in their STA-100 amplifier as phase splitter but there they operate with high input signals.

The forerunner of the EF184 was the EF80. Some two years ago there was a discussion on this forum about its usability for audio: https://www.vintage-radio.net/forum/...d.php?t=157707
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Last edited by Robert Gribnau; 25th May 2021 at 1:35 pm. Reason: typo
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